A polarizer, which is one of polarized light control devices, is a device to transmit only a vibration component in a specific direction of unpolarized light or elliptically polarized light in which an electromagnetic field vibrates in unspecific directions to obtain linearly polarized light. The polarizer is one of the most basic optical devices. The device is commonly used in an optical communication device, an optical pickup for an optical disk, a liquid crystal display, an optical application measurement, and the like. Polarizers are roughly classified into two groups by the operation type; 1 st grope directs to a polarizer which absorbs an unnecessary polarized wave and, 2nd grope directs to a polarizer which divides two orthogonal polarized wave components being incident on the same optical path into different optical paths.
Polarizers practically used at present, which performs the operation 1, a polarizer obtained by inserting dichromatic molecules such as iodine molecules into a polymer film, a glass in which needle-shaped metal particles are aligned in one direction, or the like is used. On the other hand, as the polarizer of the type 2, a polarizing prism made of a high-birefringent material such as calcite is used.
The other polarized light control device is a phase plate which delays polarized light by polarization. Namely, anisotropic materials having different refractive indexes depending on orientations are used. In general, anisotropic crystal such as quartz or rutile or a film obtained by drawing polyimide is used.
In any of the above polarized light control devices, characteristics of a polarizer or a waveplate on an aperture plane are constant within a fabricating error. More specifically, a wavelength and an optical axis in which the device operates are uniform on the aperture plane. This is because, on a manufacturing process, a device except for a device having a size of millimeters or more or centimeters or more cannot be manufactured since an anisotropic singlecrystalline material is polished or a film or glass is drawn in one direction. Each device may be cut into devices having small sizes, and the cut devices may be pasted to have different axes. However, a reduction in area of one device and a reduction in number of devices to be pasted are limited. In addition, it is difficult to accurately align the axes of small chips.
In recent years, a method of arranging small polarized light control devices in an array by fully using a lithography technique is reported.
For example, lines and spaces are processed in a metal film to form a polarizer. For example, a polarizer described in 31a-W-2 in The Japan Society of Applied Physics National Conference, 2000, spring, a polarizer described in U.S. Pat. No. 6,122,103, and a polarizer described in the following paper: (Applied Physics Letters, vol. 77, no. 7, pp. 927 to 929, August 2000) are known. These polarizers are based on the following principle. That is, since electrons in a metallic thin wire can move in a direction parallel to the thin line but cannot smoothly move in a direction perpendicular to the metallic thin wire, a polarized wave, which is parallel to the thin line, of incident light is absorbed largely more than a polarized wave in the perpendicular direction. In order to achieve a low loss and a high extinction ratio, it is required to infinitely increase an aspect ratio of the metallic thin wire. However, in fact, since the metallic thin wire has a finite width, an insertion loss does not become 0 in principle.
Similarly, lines and spaces of a transparent material form a waveplate. However, since the depth of a groove directly influence a phase difference, a groove having a high aspect ratio cannot be easily processed with high reproducibility. In addition, since the depths of grooves processed by one process cannot be changed depending on regions, a phase difference is constant at the same location. More specifically, a quarter waveplate and half waveplate cannot be simultaneously formed. An array cannot be formed by combining a phase plate and a polarizer.
For this reason, when a plurality of polarizers and a plurality of waveplates having different optical axes and different wavelengths are to be combined to each other, a large-scale apparatus which splits a light beam and uses independent devices is required. In particular, in a conventional polarization analyzer, as shown in FIG. 3, a large number of independent devices such as a light beam splitter 301, a polarized light beam splitter 302, a polarizer 303, a quarter waveplate 304, and a right-receiving device 305 are used, i.e., the number of parts is large. The analyzer is so complex that axes must be aligned at high accuracy. Actually, all the devices cannot be pasted at a 0.1° order. In addition, it is not realized that a polarizer array composed of the metal lines and spaces is mounted on a CCD camera or the like to perform polarized light image analysis because sufficient characteristics such as a high extinction ratio of the polarizer and high productivity cannot be achieved.